Straightening iron



FIG. 1 is a perspective view of a straightening iron showing my new design;

FIG. 2 is a right end view thereof;

FIG. 3 is a left end view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof. 

The ornamental design for a “straightening iron”, as shown. 